Method of preparing metallocene catalysts

ABSTRACT

Methods of preparing silica-supported catalysts useful for olefin polymerization are described. The catalysts comprise a metallocene complex. An activator mixture made from a boron acid compound and methylalumoxane is combined with either: (i) the metallocenecomplex, followed by calcined or chemically treated silica to give a supported catalyst; or (ii) calcined or chemically treated silica, followed by the metallocenecomplex to give a supported catalyst. The methods provide active supported catalysts.

The invention relates to ways to prepare metallocene catalysts usefulfor polymerizing olefins.

While Ziegler-Natta catalysts are a mainstay for polyolefin manufacture,single-site catalysts represent the industry's future. These catalystsopen possibility to produce polymers with improved physical properties.The improved properties include controlled molecular weightdistribution, reduced low molecular weight extractables, enhancedincorporation of α-olefin comonomers, lower polymer density, controlledcontent and distribution of long-chain branching, and modified meltrheology and relaxation characteristics.

A well known kind of single-site catalyst leading to a variety ofpolyolefin products is a metallocene catalyst which generally isactivated with MAO. In special processes, such as e.g. the Spheripolprocess this kind of catalyst systems tend to cause reactor fouling dueto leaching of activated metallocene in the presence of alkyl aluminum,which is used as scavenger. Thus in these processes, MAO activatedmetallocene catalysts require the absence of any scavenger and thereforelack in catalyst mileage due to traces of poisons (H₂O, CO₂, CO etc.) inthe polymerization process. Increasing the mileage capability androbustness of the metallocene MAO catalyst is most desirable to improvemetallocene MAO catalyst efficiency.

Therefore, it is an object of the present invention to provide aparticularly valuable method for preparing supported catalyst systemscomprising metallocenes which provide high activity for polymerizingolefins without use of alkyl aluminum.

The invention relates to methods for preparing supported catalystsuseful for polymerizing olefins. The catalysts comprise a metallocenecomplex that incorporates a cyclopentadienyl ligand. In the inventivemethod, a boron acid compound having Lewis acidity is first combinedwith excess alkylalumoxane to produce an activator mixture. Thisactivator mixture is then combined with either: (i) the metallocenecomplex described above, followed by calcined or chemically treatedsilica to give a supported catalyst; or (ii) calcined or chemicallytreated silica, followed by the metallocene complex to give a supportedcatalyst. The supported catalysts allow efficient polymerization toproduce polyolefins without leading to any leaching of activatedmetallocene.

Catalysts prepared by the method of the invention are particularlyuseful for polymerizing olefins. They comprise an activated metallocenecomplex, preferably, a complex of a transition metal of group 4 of thePeriodic Table of the Elements. Group 4 metals include zirconium,titanium, and hafnium. Zirconium and hafnium are preferred. Zirconium isparticularly preferred.

The first step in the inventive method involves preparation of anactivator mixture. This mixture is produced by combining a boron acidcompound having Lewis acidity with excess alkylalumoxane.

Suitable boron acid compounds are borinic acids and boronic acids, andmixtures thereof. Perfluorinated organoboron acid compounds arepreferred. Specific examples include bis(pentafluorophenyl)borinic acid,pentafluorophenylboronic acid, and the like. Especially preferred isbis(pentafluorophenyl)borinic acid.

Suitable alkylalumoxanes are well known and many are commerciallyavailable as solutions in hydrocarbon solvents from Albemarle, AkzoNobel, and other suppliers. Examples include methylalumoxane,ethylalumoxane, etc. Methylalumoxanes, such as MAO, MMAO, or PMAO areparticularly preferred.

The alkylalumoxane is used in excess compared with the amount of boronacid compound. Preferably, the alkylalumoxane and boron acid compoundare used in amounts that provide an aluminum to boron (Al/B) molar ratiowithin the range of 2 to 50, more preferably from 5 to 40, mostpreferably from 8 to 35.

In one method of the invention, the activator mixture is combined with ametallocene complex, followed by calcined or chemically treated silicato give the supported catalyst. In a second method, the order isreversed, i.e., the activator mixture is combined first with thecalcined or chemically treated silica, followed by the metallocenecomplex.

Thus, suitable metallocene complexes include a cyclopentadienyl ligand.

The metallocenes suitable for the catalyst systems produced by themethod of the present invention are metallocenes of transition metals ofgroup 3, 4, 5 or 6 of the Periodic Table of the Elements, preferable oftransition metals of group 4 of the Periodic Table of the Elements. Morepreferred are metallocene compounds having two different π-ligands.

Particular preference is given to catalyst systems based on metallocenecompounds of the formula (I),

where

-   M is zirconium, hafnium or titanium, preferably zirconium,-   X are identical or different and are each, independently of one    another, hydrogen or halogen or an —R, —OR, —OSO₂CF₃, —OCOR, —SR,    —NR₂ or —PR₂ group, where R is linear or branched C₁-C₂₀-alkyl,    C₃-C₂₀-cycloalkyl which may be substituted by one or more    C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or    C₇-C₂₀-arylalkyl and may contain one or more heteroatoms of groups    13-17 of the Periodic Table of the Elements or one or more    unsaturated bonds, preferably C₁-C₁₀-alkyl such as methyl, ethyl,    n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,    n-pentyl, n-hexyl, n-heptyl or n-octyl or C₃-C₂₀-cycloalkyl such as    cyclopentyl or cyclohexyl, where the two radicals X may also be    joined to one another and preferably form a C₄-C₄₀-dienyl ligand, in    particular a 1,3-dienyl ligand, or an —OR′O— group in which the    substituent R′ is a divalent group selected from the group    consisting of C₁-C₄₀-alkylidene, C₆-C₄₀-arylidene,    C₇-C₄₀-alkylarylidene and C₇-C₄₀-arylalkylidene,    -   where X is preferably a halogen atom or an —R or —OR group or        the two radicals X form an —OR′O— group and X is particularly        preferably chlorine or methyl,-   L is a divalent bridging group selected from the group consisting of    C₁-C₂₀-alkylidene radicals, C₃-C₂₀-cycloalkylidene radicals,    C₆-C₂₀-arylidene radicals, C₇-C₂₀-alkylarylidene radicals and    C₇-C₂₀-arylalkylidene radicals, which may contain heteroatoms of    groups 13-17 of the Periodic Table of the Elements, or a silylidene    group having up to 5 silicon atoms, e.g. —SiMe₂- or —SiPh₂-, where L    preferably is a radical selected from the group consisting of    —SiMe₂-, —SiPh₂-, —SiPhMe—, —SiMe(SiMe₃)—, —CH₂—, —(CH₂)₂—, —(CH₂)₃—    and —C(CH₃)₂—,-   R¹ is linear or branched C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl which may    be substituted by one or more C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl,    C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and may contain one or more    heteroatoms of groups 13-17 of the Periodic Table of the Elements or    one or more unsaturated bonds, where R¹ is preferably unbranched in    the a position and is preferably a linear or branched C₁-C₁₀-alkyl    group which is unbranched in the a position, in particular a linear    C₁-C₄-alkyl group such as methyl, ethyl, n-propyl or n-butyl,-   R² is a group of the formula —C(R³)₂R⁴, where-   R³ are identical or different and are each, independently of one    another, linear or branched C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl which    may be substituted by one or more C₁-C₁₀-alkyl radicals,    C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and may contain    one or more heteroatoms of groups 13-17 of the Periodic Table of the    Elements or one or more unsaturated bonds, or two radicals R³ may be    joined to form a saturated or unsaturated C₃-C₂₀-ring,    -   where R³ is preferably a linear C₁-C₁₀-alkyl group, and-   R⁴ is hydrogen, linear or branched C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl    which may be substituted by one or more C₁-C₁₀-alkyl radicals,    C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and may contain    one or more heteroatoms of groups 13-17 of the Periodic Table of the    Elements or one or more unsaturated bonds,    -   where R⁴ is preferably hydrogen,-   R⁵ are identical or different and are each, independently of one    another, hydrogen or halogen or linear or branched C₁-C₂₀-alkyl,    C₃-C₂₀-cycloalkyl which may be substituted by one or more    C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or    C₇-C₂₀-arylalkyl and may contain one or more heteroatoms of groups    13-17 of the Periodic Table of the Elements or one or more    unsaturated bonds,    -   where R⁵ is preferably hydrogen or a linear or branched        C₁-C₁₀-alkyl group, in particular hydrogen, and-   R⁶ are identical or different and are each, independently of one    another hydrogen, linear or branched C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl    which may be substituted by one or more C₁-C₁₀-alkyl radicals,    C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and may contain    one or more heteroatoms of groups 13-17 of the Periodic Table of the    Elements or one or more unsaturated bonds, or the two radicals R⁶    may be joined to form together with the atoms connecting them a    saturated or unsaturated C₅-C₂₀ ring, where preferably R⁶ is    hydrogen or two R⁶ preferably are joined to form a saturated or    unsaturated C₅-C₁₄ ring,-   R⁷ are identical or different and are each, independently of one    another, halogen or linear or branched C₁-C₂₀-alkyl,    C₃-C₂₀-cycloalkyl which may be substituted by one or more    C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or    C₇-C₂₀-arylalkyl and may contain one or more heteroatoms of groups    13-17 of the Periodic Table of the Elements or one or more    unsaturated bonds,    -   where R⁷ is preferably an aryl group of the formula (II),

where

-   R⁸ are identical or different and are each, independently of one    another, hydrogen or halogen or linear or branched C₁-C₂₀-alkyl,    C₃-C₂₀-cycloalkyl which may be substituted by one or more    C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or    C₇-C₂₀-arylalkyl and may contain one or more heteroatoms of groups    13-17 of the Periodic Table of the Elements or one or more    unsaturated bonds, or two radicals R⁸ may be joined to form a    saturated or unsaturated C₃-C₂₀ ring,    -   where R⁸ is preferably a hydrogen atom, and-   R⁹ is hydrogen or halogen or linear or branched C₁-C₂₀-alkyl,    C₃-C₂₀-cycloalkyl which may be substituted by one or more    C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or    C₇-C₂₀-arylalkyl and may contain one or more heteroatoms of groups    13-17 of the Periodic Table of the Elements or one or more    unsaturated bonds,    -   where R⁸ is preferably a branched alkyl group of the formula        —C(R¹⁰)₃, where-   R¹⁰ are identical or different and are each, independently of one    another, a linear or branched C₁-C₆-alkyl group or two or three of    the radicals R¹⁰ are joined to form one or more ring systems.

Examples of preferred metallocene compounds are

-   dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(4″-tert-butylphenyl)indenyl)zirconium    dichloride,-   dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(4″-tert-butylphenyl)indenyl)zirconium    dimethyl,-   dimethylsilanediyl    (2-ethyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(4″-tert-butylphenyl)indenyl)zirconium    dichloride,-   dimethylsilanediyl    (2-ethyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(4″-tert-butylphenyl)indenyl)zirconium    dimethyl-   dimethylsilanediyl    (2-methyl-4-phenyl-1-indenyl)(2-isopropyl-4-(4″-tert-butylphenyl)-1-indenyl)zirconium    dichloride,-   dimethylsilanediyl    (2-methyl-4-phenyl-1-indenyl)(2-isopropyl-4-(4″-tert-butylphenyl)-1-indenyl)zirconium    dimethyl-   dimethylsilanediyl    (2-isopropyl-4-(4′-tert-butylphenyl)indenyl)(2-methyl-4,5-benzindenyl)zirconium    dichloride,-   dimethylsilanediyl    (2-isopropyl-4-(4′-tert-butylphenyl)indenyl)(2-methyl-4,5-benzindenyl)zirconium    dimethyl-   dimethylsilanediyl    (2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(1-naphthyl)indenyl)zirconium    dichloride,-   dimethylsilanediyl    (2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(1-naphthyl)indenyl)zirconium    dimethyl-   dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-phenylindenyl)zirconium    dichloride,-   dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-phenylindenyl)zirconium    dimethyl,-   dimethylsilanediyl(2-ethyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-phenyl)indenyl)zirconium    dichloride,-   dimethylsilanediyl(2-ethyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-phenyl)indenyl)zirconium    dichloride,-   dimethylsilanediyl(2-isopropyl-4-(4′-tert-butylphenyl)indenyl)(2-methyl-4-(1-naphthyl)indenyl)zirconium    dichloride,-   dimethylsilanediyl(2-isopropyl-4-(4′-tert-butyl    phenyl)indenyl)(2-methyl-4-(1-naphthyl)indenyl)zirconium dimethyl    and mixtures thereof.

Catalysts made by the method of the invention are preferably supportedon silica. The silica generally has a surface area in the range of about10 to about 1000 m²/g, preferably from about 50 to about 800 m²/g andmore preferably from about 200 to about 700 m²/g. Preferably, the porevolume of the silica is in the range of about 0.05 to about 4.0 mL/g,more preferably from about 0.08 to about 3.5 mL/g, and most preferablyfrom about 0.1 to about 3.0 mL/g. Preferably, the average particle sizeof the silica is in the range of about 1 to about 500 μm, morepreferably from about 2 to about 200 μm, and most preferably from about2 to about 45 μm. The average pore diameter is typically in the range ofabout 0.05 to about 10 μm, preferably about 0.1 to about 5 μm, and mostpreferably about

0.2 to about 3.5 μm.

The silica is calcined, chemically treated, or both prior to use toreduce the concentration of surface hydroxyl groups. Calcinationinvolves heating the support in a dry atmosphere at elevatedtemperature, preferably greater than 200° C., more preferably greaterthan 500° C., and most preferably from about 250 to about 800° C., priorto use. A variety of different chemical treatments can be used,including reaction with organoaluminum, -magnesium, -silicon, or -boronacid compounds. See, for example, the techniques described in U.S. Pat.No. 6,211,311, the teachings of which are incorporated herein byreference. Preferably, the silica is simply calcined prior to use.

Although there are many ways to combine complexes and activators, it isusually far from clear which methods will prove most satisfactory for aparticular type of olefin polymerization catalyst. We surprisingly foundthat metallocene complexes are effectively activated using combinationsof boron acid compounds and alkylalumoxanes when the activatorcomponents are precombined. Later combination with complex and calcinedor chemically treated silica as outlined above provides catalysts withexcellent activities for polymerizing olefins.

The following examples merely illustrate the invention. Those skilled inthe art will recognize many variations that are within the spirit of theinvention and scope of the claims.

EXAMPLES

The weight average molar mass M_(w) and the molar mass distributionM_(w)/M_(n) were determined by gel permeation chromatography (GPC) at145° C. in 1,2,4-trichlorobenzene using a GPC apparatus 150C fromWaters. The data were evaluated using the Win-GPC software fromHS-Entwicklungsgesellschaft für wissenschaftliche Hard- and SoftwarembH, Ober-Hilbersheim. Calibration of the columns was carried out bymeans of polypropylene standards having molar masses of from 100 to 10⁷g/mol.

The melting points were determined by means of DSC (differentialscanning calorimetry). The measurement was carried out in accordancewith ISO standard 3146 using a first heating at a heating rate of 20° C.per minute to 200° C., a dynamic crystallization at a cooling rate of20° C. per minute down to 25° C. and a second heating at a heating rateof 20° C. per minute back to 200° C. The melting point is then thetemperature at which the enthalpy vs. temperature curve measured in thesecond heating displays a maximum.

Example 1 a) Synthesis of the Modified MAO

80 ml of MAO (30 wt % in toluene) were diluted with 100 ml of tolueneand cooled to 0° C. In a separate flask, 18.4 g ofbis(pentafluorophenyl)borinic acid were dissolved in 250 ml of tolueneand added to the MAO/toluene solution in such a way, that the reactiontemperature did not exceed 2° C. After complete addition of thebis(pentafluorophenyl)borinic acid the reaction mixture was filteredafter being stirred for another hour at 0° C. The filtrate was kept overnight in a refrigerator at 4° C.

b) Synthesis of the Metallocene Catalyst A

10 g of silica support (Grace XPO2326, dried at 130° C. for 6 h) weresuspended in 100 ml of toluene. The suspension was cooled to 0° C. andtreated with 130 ml of the modified MAO solution described in Example1a. During the addition, the reaction temperature was kept at 0° C. andafterwards raised to 25° C. After continuous stirring for 1 hour, thesuspension was filtered and washed 3 times with 100 ml portions oftoluene and again suspended in 100 ml of toluene. In a separate flask248 mg ofrac-dimethyl-silanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(4′-tertbutyl-phenyl)indenyl)zirconiumdimethyl were dissolved in 40 ml of toluene and at ambient temperaturetreated with 13 ml of the modified MAO solution described in Example 1a.The reaction mixture was stirred for 1 hour at ambient temperature andafter that added to the silica support suspension at 15° C. Thetemperature was raised to 40° C. and stirred for 2 hours. Subsequentlythe suspension was filtered, suspended in 100 ml of toluene, stirred for30 min at 60° C. This procedure was repeated 2 times. At last theremaining solid was suspended in 100 ml of n-heptane, stirred for 30 minat 60° C. and filtered. The residue was dried in vacuum until its weightremained constant. 19 g of a free flowing powder were obtained.

c) Polymerization

A dry 14 l reactor was flushed 3 times with nitrogen and 3 times withpropylene. 10 ml (19 mmol) of a 1.9 M triisobutylaluminum solution inheptane were placed in the reactor, which was subsequently charged with306 mg of hydrogen and 2.5 kg of propylene at 30° C. A suspension of 85mg of neat catalyst A prepared in example 1b) in 2 ml of hexane weresubsequently rinsed into the reactor with 1 kg of propylene. Thereaction temperature was set at 25° C. for 10 min and subsequentlyraised to 65° C. at which the polymerization occurred for 1 hour. Thereaction was stopped by venting the remaining propylene. 2280 g of afinely divided polymer were obtained. The interior walls of the reactordisplayed no deposits. The catalyst activity was 26.8 kg of PP/g ofcatalyst solid per hour. The polypropylene obtained had the followingproperties: M_(w)=274.000 g/mol, M_(w)/M_(n)=3.7, melting point=156° C.

Example 2 a) Synthesis of the Modified MAO

55 ml of MAO (30 wt % in toluene) were diluted with 150 ml of tolueneand cooled to 0° C. In a separate flask, 6.3 g ofbis(pentafluorophenyl)borinic acid were dissolved in 90 ml of tolueneand added to the MAO/toluene solution in such a way, that the reactiontemperature did not exceed 2° C. After complete addition of thebis(pentafluorophenyl)borinic acid the reaction mixture was filteredafter being stirred for another hour at 0° C. The filtrate was kept overnight in a refrigerator at 4° C.

b) Synthesis of the Metallocene Catalyst B

10 g of silica support (Grace XPO2326, dried at 130° C. for 6 h) weresuspended in 100 ml of toluene. The suspension was cooled to 0° C. andtreated with 153 ml of the modified MAO solution described in Example2a. During the addition, the reaction temperature was kept at 0° C. andafterwards raised to 25° C. After continuous stirring for 1 hour, thesuspension was filtered and washed 3 times with 100 ml portions oftoluene and again suspended in 100 ml of toluene. In a separate flask248 mg ofrac-dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(4′-tetrbutylphenyl)indenyl)zirconiumdimethyl were dissolved in 40 ml of toluene and at ambient temperaturetreated with 15.3 ml of the modified MAO solution described in Example2a. The reaction mixture was stirred for 1 hour at ambient temperatureand after that added to the silica support suspension at 15° C. Thetemperature was raised to 40° C. and stirred for 2 hours. Subsequentlythe suspension was filtered, suspended in 100 ml of toluene, stirred for30 min at 60° C. This procedure was repeated 2 times. The residue wasdried in vacuum until its weight remained constant. 15 g of a freeflowing powder were obtained.

c) Polymerization

A dry 14 l reactor was flushed 3 times with nitrogen and 3 times withpropylene and subsequently charged with 306 mg of hydrogen and 2.5 kg ofpropylene at 30° C. A suspension of 166 mg of neat catalyst B preparedin example 2b) in 2 ml of hexane were subsequently rinsed into thereactor with 1 kg of propylene. The reaction temperature was set at 25°C. for 10 min and subsequently raised to 65° C. at which thepolymerization occurred for 1 hour. The reaction was stopped by ventingthe remaining propylene. 1380 g of a finely divided polymer wereobtained. The interior walls of the reactor displayed no deposits. Thecatalyst activity was 8.3 kg of PP/g of catalyst solid per hour. Thepolypropylene obtained had the following properties: M_(w)=146.000g/mol, M_(w)/M_(n)=3.3, melting point=154° C.

Example 3 a) Synthesis of the Modified MAO

55 ml of MAO (30 wt % in toluene) were diluted with 150 ml of tolueneand cooled to 0° C. In a separate flask, 3.15 g ofbis(pentafluorophenyl)borinic acid were dissolved in 90 ml of tolueneand added to the MAO/toluene solution in such a way, that the reactiontemperature did not exceed 2° C. After complete addition of thebis(pentafluorophenyl)borinic acid the reaction mixture was filteredafter being stirred for another hour at 0° C. The filtrate was kept overnight in a refrigerator at 4° C.

b) Synthesis of the Metallocene Catalyst C

10 g of silica support (Grace XPO2326, dried at 130° C. for 6 h) weresuspended in 100 ml of toluene. The suspension was cooled to 0° C. andtreated with 115 g of the modified MAO solution described in Example 3a.During the addition, the reaction temperature was kept at 0° C. andafterwards raised to 25° C. After continuous stirring for 1 hour, thesuspension was filtered and washed 3 times with 100 ml portions oftoluene and again suspended in 100 ml of toluene. In a separate flask248 mg ofrac-dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(4′-tetrbutylphenyl)indenyl)zirconiumdimethyl were dissolved in 40 ml of toluene and at ambient temperaturetreated with 11.5 g of the modified MAO solution described in Example3a. The reaction mixture was stirred for 1 hour at ambient temperatureand after that added to the silica support suspension at 15° C. Thetemperature was raised to 40° C. and stirred for 2 hours. Subsequentlythe suspension was filtered, suspended in 100 ml of toluene, stirred for30 min at 60° C. This procedure was repeated 2 times. The residue wasdried in vacuum until its weight remained constant. 15 g of a freeflowing powder were obtained.

c) Polymerization

A dry 14 l reactor was flushed 3 times with nitrogen and 3 times withpropylene. 10 ml (19 mmol) of a 1.9 M triisobutylaluminum solution inheptane were placed in the reactor, which was subsequently charged with306 mg of hydrogen and 2.5 kg of propylene at 30° C. A suspension of 93mg of neat catalyst C prepared in example 2b) in 2 ml of hexane weresubsequently rinsed into the reactor with 1 kg of propylene. Thereaction temperature was set at 25° C. for 10 min and subsequentlyraised to 65° C. at which the polymerization occurred for 1 hour. Thereaction was stopped by venting the remaining propylene. 1917 g of afinely divided polymer were obtained. The interior walls of the reactordisplayed no deposits. The catalyst activity was 20.6 kg of PP/g ofcatalyst solid per hour. The polypropylene obtained had the followingproperties: M_(w)=175.000 g/mol, M_(w)/M_(n)=2.5, melting point=156° C.

Example 4 a) Synthesis of the Modified MAO

30 ml of MAO (30 wt % in toluene) were diluted with 50 ml of toluene andcooled to 0° C. In a separate flask, 6.9 g ofbis(pentafluorophenyl)borinic acid were dissolved in 150 ml of tolueneand added to the MAO/toluene solution in such a way, that the reactiontemperature did not exceed 2° C. After complete addition of thebis(pentafluorophenyl)borinic acid the reaction mixture was filteredafter being stirred for another hour at 0° C. The filtrate was kept overnight in a refrigerator at 4° C.

b) Synthesis of the Metallocene Catalyst D

15 g of silica support (Grace XPO2326, dried at 130° C. for 6 h) weresuspended in 100 ml of toluene. The suspension was cooled to 0° C. andtreated with 165 g of the modified MAO solution described in Example 4a.During the addition, the reaction temperature was kept at 0° C. andafterwards raised to 25° C. After continuous stirring for 1 hour, thesuspension was filtered and washed 3 times with 100 ml portions oftoluene and again suspended in 100 ml of toluene. In a separate flask316 mg ofrac-dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(4′-tetrbutylphenyl)indenyl)zirconiumdimethyl were dissolved in 50 ml of toluene and at ambient temperaturetreated with 21.4 g of the modified MAO solution described in Example4a. The reaction mixture was stirred for 1 hour at ambient temperatureand after that added to the silica support suspension at 15° C. Thetemperature was raised to 40° C. and stirred for 2 hours. Subsequentlythe suspension was filtered, suspended in 100 ml of toluene, stirred for30 min at 60° C. This procedure was repeated 2 times. The residue wasdried in vacuum until its weight remained constant. 23 g of a freeflowing powder were obtained.

c) Polymerization

A dry 14 l reactor was flushed 3 times with nitrogen and 3 times withpropylene. 10 ml (19 mmol) of a 1.9 M triisobutylaluminum solution inheptane were placed in the reactor, which was subsequently charged with306 mg of hydrogen and 2.5 kg of propylene at 30° C. A suspension of 101mg of neat catalyst D prepared in example 4b) in 2 ml of hexane weresubsequently rinsed into the reactor with 1 kg of propylene. Thereaction temperature was set at 25° C. for 10 min and subsequentlyraised to 65° C. at which the polymerization occurred for 1 hour. Thereaction was stopped by venting the remaining propylene. 1730 g of afinely divided polymer were obtained. The interior walls of the reactordisplayed no deposits. The catalyst activity was 17.1 kg of PP/g ofcatalyst solid per hour. The polypropylene obtained had the followingproperties: M_(w)=196.000 g/mol, M_(w)/M_(n)=3.0, melting point=156° C.

Example 5 a) Synthesis of the Modified MAO

68.5 ml of MAO (30 wt % in toluene) were diluted with 100 ml of tolueneand cooled to 0° C. In a separate flask, 7.85 g ofbis(pentafluorophenyl)borinic acid were dissolved in 200 ml of tolueneand added to the MAO/toluene solution in such a way, that the reactiontemperature did not exceed 2° C. After complete addition of thebis(pentafluorophenyl)borinic acid the reaction mixture was filteredafter being stirred for another hour at 0° C. The filtrate was kept overnight in a refrigerator at 4° C.

b) Synthesis of the Metallocene Catalyst E

15 g of silica support (Grace XPO2326, dried at 130° C. for 6 h) weresuspended in 100 ml of toluene. The suspension was cooled to 0° C. andtreated with 116 g of the modified MAO solution described in Example 5a.During the addition, the reaction temperature was kept at 0° C. andafterwards raised to 25° C. After continuous stirring for 1 hour, thesuspension was filtered and washed 3 times with 100 ml portions oftoluene and again suspended in 100 ml of toluene. In a separate flask315 mg ofrac-dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(4′-tetrbutylphenyl)indenyl)zirconiumdimethyl were dissolved in 50 ml of toluene and at ambient temperaturetreated with 15.2 g of the modified MAO solution described in Example5a. The reaction mixture was stirred for 1 hour at ambient temperatureand after that added to the silica support suspension at 15° C. Thetemperature was raised to 40° C. and stirred for 2 hours. Subsequentlythe suspension was filtered, suspended in 100 ml of toluene, stirred for30 min at 40° C. This procedure was repeated 2 times. The residue wasdried in vacuum until its weight remained constant. 24 g of a freeflowing powder were obtained.

c) Polymerization

A dry 14 l reactor was flushed 3 times with nitrogen and 3 times withpropylene. 10 ml (19 mmol) of a 1.9 M triisobutylaluminum solution inheptane were placed in the reactor, which was subsequently charged with306 mg of hydrogen and 2.5 kg of propylene at 30° C. A suspension of 82mg of neat catalyst E prepared in example 4b) in 2 ml of hexane weresubsequently rinsed into the reactor with 1 kg of propylene. Thereaction temperature was set at 25° C. for 10 min and subsequentlyraised to 65° C. at which the polymerization occurred for 1 hour. Thereaction was stopped by venting the remaining propylene. 1761 g of afinely divided polymer were obtained. The interior walls of the reactordisplayed no deposits. The catalyst activity was 21.5 kg of PP/g ofcatalyst solid per hour. The polypropylene obtained had the followingproperties: M_(w)=197.000 g/mol, M_(w)/M_(n)=3.1, melting point=156° C.

Comparative Example 1 a) Synthesis of the Metallocene Catalyst F

Catalyst F corresponds to catalyst A, but without borinic acid.

b) Polymerization

A dry 14 l reactor was flushed 3 times with nitrogen and 3 times withpropylene. 10 ml (19 mmol) of a 1.9 M triisobutylaluminum solution inheptane were placed in the reactor, which was subsequently charged with306 mg of hydrogen and 2.5 kg of propylene at 30° C. A suspension of 158mg of neat catalyst F in 2 ml of hexane was subsequently rinsed into thereactor with 1 kg of propylene. The reaction temperature was set at 25°C. for 10 min and subsequently raised to 65° C. at which thepolymerization occurred for 1 hour. The reaction was stopped by ventingthe remaining propylene. 2366 g of a finely divided polymer wereobtained. The interior walls of the reactor displayed no deposits. Thecatalyst activity was 15.0 kg of PP/g of catalyst solid per hour. Thepolypropylene obtained had the following properties: M_(w)=244.000g/mol, M_(w)/M_(n)=3.2, melting point=156° C.

c) Polymerization without Scavenger

A dry 14 l reactor was flushed 3 times with nitrogen and 3 times withpropylene and subsequently charged with 306 mg of hydrogen and 2.5 kg ofpropylene at 30° C. A suspension of 459 mg of neat catalyst F preparedin the comparative example 1 in 2 ml of hexane was subsequently rinsedinto the reactor with 1 kg of propylene. The reaction temperature wasset at 25° C. for 10 min and subsequently raised to 65° C. at which thepolymerization occurred for 1 hour. The reaction was stopped by ventingthe remaining propylene. 2300 g of a finely divided polymer wereobtained. The interior walls of the reactor displayed no deposits. Thecatalyst activity was 5.0 kg of PP/g of catalyst solid per hour. Thepolypropylene obtained had the following properties: M_(w)=282.000g/mol, M_(w)/M_(n)=3.7, melting point=156° C.

Example 6 a) Synthesis of the Modified MAO

50 ml of MAO (30 wt % in toluene) were diluted with 200 ml of tolueneand cooled to 0° C. In a separate flask, 11.5 g ofbis(pentafluorophenyl)borinic acid were dissolved in 100 ml of tolueneand added to the MAO/toluene solution in such a way, that the reactiontemperature did not exceed 2° C. After complete addition of thebis(pentafluorophenyl)borinic acid the reaction mixture was filteredafter being stirred for another hour at 0° C. The filtrate was kept overnight in a refrigerator at 4° C.

b) Synthesis of the Metallocene Catalyst G

18 g of silica support (Grace XPO2485, dried at 130° C. for 6 h) weresuspended in 100 ml of toluene. The suspension was cooled to 0° C. andtreated with 304 ml of the modified MAO solution described in Example6a. During the addition, the reaction temperature was kept at 0° C. andafterwards raised to 25° C. After continuous stirring for 1 hour, thesuspension was filtered and washed 3 times with 100 ml portions oftoluene and again suspended in 100 ml of toluene. In a separate flask347 mg ofrac-dimethylsilanediyl-bis(2-methyl-(4-phenyl)indenyl)zirconiumdichloride were suspended in 41 ml of toluene and at ambient temperaturetreated with 32 ml of the modified MAO solution described in Example 6a.The reaction mixture was stirred for 1 hour at ambient temperature andafter that added to the silica support suspension at 15° C. Thetemperature was raised to 40° C. and stirred for 2 hours. Subsequentlythe suspension was filtered, suspended in 100 ml of toluene, stirred for30 min at 60° C. At last the remaining solid was suspended in 100 ml ofn-heptane, stirred for 30 min at 60° C. and filtered. The residue wasdried in vacuum until its weight remained constant. 32 g of a freeflowing powder were obtained.

c) Polymerization

A dry 14 l reactor was flushed 3 times with nitrogen and 3 times withpropylene. 10 ml (19 mmol) of a 1.9 M triisobutylaluminum solution inheptane were placed in the reactor, which was subsequently charged with306 mg of hydrogen and 2.5 kg of propylene at 30° C. A suspension of 98mg of neat catalyst G prepared in example 6b) in 2 ml of hexane weresubsequently rinsed into the reactor with 1 kg of propylene. Thereaction temperature was set at 25° C. for 10 min and subsequentlyraised to 65° C. at which the polymerization occurred for 1 hour. Thereaction was stopped by venting the remaining propylene. 2719 g of afinely divided polymer were obtained. The interior walls of the reactordisplayed no deposits. The catalyst activity was 27.7 kg of PP/g ofcatalyst solid per hour. The polypropylene obtained had the followingproperties: M_(w)=544.000 g/mol, M_(w)/M_(n)=4.8, melting point=150° C.

[Al] [B] [Zr] H₂ Activity Mw Mw/ Tm₂ Example catalyst wt. % wt..% μmol/gTiBA mg Kg/gh g/mol Mn ° C. 1c A 14.6 0.78 40 yes 306 26.8 274.000 3.7156 2c B 16.6 0.44 40 no 306 8.3 146.000 3.3 154 3c C 17.9 0.24 40 yes306 20.6 175.000 2.5 156 4c D 12.1 0.65 30 yes 306 17.1 196.000 3.0 1565c E 13.6 0.36 30 yes 306 21.5 197.000 3.1 156 CE 1b F 18.7 0 40 yes 30615.0 244.000 3.2 156 CE 1c F 18.7 0 40 no 306 5.0 282.000 3.7 156 6c G14.6 0.79 30 yes 306 27.7 544.000 4.8 150

1. A method of preparing a supported catalyst useful for polymerizingolefins, comprising: (a) combining a boron acid compound with excessalkylalumoxane to produce an activator mixture; and (b) combining theactivator mixture with either: (i) a metallocene complex, followed bycalcined or chemically treated silica to give the supported catalyst; or(ii) calcined or chemically treated silica, followed by a metallocenecomplex to give the supported catalyst.
 2. The method according to claim1 wherein the alkylalumoxane and boron acid compound are used in amountsthat provide an aluminum to boron (Al/B) molar ratio within the range of2:1 to 50:1.
 3. The method according to claim 2 wherein the Al/B molarratio is within the range of 5:1 to 40:1.
 4. The method according toclaim 1 wherein the alkylalumoxane is methyl-alumoxane.
 5. The methodaccording to claim 1 wherein the boron acid compound is selected fromthe group consisting of boronic acids and borinic acids.
 6. The methodaccording to claim 1 wherein the metallocene complex corresponds toformula (I),

where M is zirconium, hafnium or titanium, X are identical or differentand are each, independently of one another, hydrogen or halogen or an—R, —OR, —OSO₂CF₃, —OCOR, —SR, —NR₂ or —PR₂ group, where R is linear orbranched C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl which may be substituted by oneor more C₁-C₁₀-alkyl radicals, or C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl,C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and may contain one or moreheteroatoms of groups 13-17 of the Periodic Table of the Elements or oneor more unsaturated bonds, where the two radicals X may also be joinedto one another, L is a divalent bridging group selected from the groupconsisting of C₁-C₂₀-alkylidene radicals, C₃-C₂₀-cycloalkylideneradicals, C₆-C₂₀-arylidene radicals, C₇-C₂₀-alkylarylidene radicals andC₇-C₂₀-arylalkylidene radicals, which may contain heteroatoms of groups13-17 of the Periodic Table of the Elements, or a silylidene grouphaving up to 5 silicon atoms, R¹ is linear or branched C₁-C₂₀-alkyl,C₃-C₂₀-cycloalkyl which may be substituted by one or more C₁-C₁₀-alkylradicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and maycontain one or more heteroatoms of groups 13-17 of the Periodic Table ofthe Elements or one or more unsaturated bonds, R² is a group of theformula —C(R³)₂R⁴, where R³ are identical or different and are each,independently of one another, linear or branched C₁-C₂₀-alkyl,C₃-C₂₀-cycloalkyl which may be substituted by one or more C₁-C₁₀-alkylradicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and maycontain one or more heteroatoms of groups 13-17 of the Periodic Table ofthe Elements or one or more unsaturated bonds, or two radicals R³ may bejoined to form a saturated or unsaturated C₃-C₂₀-ring, and R⁴ ishydrogen, or linear or branched C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl whichmay be substituted by one or more C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl,C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and may contain one or moreheteroatoms of groups 13-17 of the Periodic Table of the Elements or oneor more unsaturated bonds, R⁵ are identical or different and are each,independently of one another, hydrogen or halogen or linear or branchedC₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl which may be substituted by one or moreC₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyland may contain one or more heteroatoms of groups 13-17 of the PeriodicTable of the Elements or one or more unsaturated bonds, and R⁶ areidentical or different and are each, independently of one anotherhydrogen, linear or branched C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl which maybe substituted by one or more C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl,C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and may contain one or moreheteroatoms of groups 13-17 of the Periodic Table of the Elements or oneor more unsaturated bonds, or the two radicals R⁶ may be joined to formtogether with the atoms connecting them a saturated or unsaturatedC₅-C₂₀ ring, R⁷ are identical or different and are each, independentlyof one another, halogen or linear or branched C₁-C₂₀-alkyl,C₃-C₂₀-cycloalkyl which may be substituted by one or more C₁-C₁₀-alkylradicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and maycontain one or more heteroatoms of groups 13-17 of the Periodic Table ofthe Elements or one or more unsaturated bonds.
 7. Catalyst prepared by amethod according to claim 1.